Road adhesion indicator for automotive vehicles



@Ct 5, i954 R. c. L LucAs ROAD ADHESION INDICATOR EDR .moMDIIvE VEHICLESs she'ets-sheet 1 Filed Nov. 6, l95

@CL 5, 1954 R C, L LUCAS 2,690,668

ROAD ADHESION INDICATOR FOR AUTOMOTIVE VEHICLES Filed Nov. 6, 1950 6Sheets-Sheet 2 22@ Zzzvzzio J. CILLLLCQS Oct 5, 1954 R. c. l.. LUCAS2,690,568

ROAD ADHESION INDICATOR FOR AUTOMOTIVE VEHICLES Filed Nov. 6, 195C 6Sheetsheet 3 Oct. 5, 1954 R. c. L. LUCAS ROAD ADHESION INDICATOR FORAUTOMOTIVE VEHICLES 6 Sheets-Sheet 4 Filed NOV. 6, 1950 Oct. 5, 1954 R.c. L LUCAS 2,690,668

l ROAD ADHESION INDICATOR FOR AUTOMOTIVE VEHICLES Filed Nov. 6, 1950 6Sheets-Sheet' Mm MM Z22/velato@ 5, @..LLu/c/ Oct- 5, l954 R. c. LUCAS2,690,568

ROAD ADHESION INDICATOR FOR AUTOMOTIVE VEHICLES y I Filed Nov. 6, 1950 6Sheets-Sheet 6 Patented Oct. 5, 1954 PATENT OFFICE ROAD ADHESIONINDICATOR FOR AUTOMOT'IVE VEHICLES l Ciaims.

This patent application is a continuation in part of my earlier U. S.patent application Serial No. 121,758 filed on October '17, 1949, forAdherence Indicating Instrument for Use on Motorcars, and now abandoned,and certain parts of the present application will be found in theearlier application.

This invention relates to an apparatus adapted to indicate whether thewheels of an automotive vehicle are about to skid or whether a skid islikely to occur on account of insuiiicient adhesion of the Wheels to theroad surface.

Adhesion indicators have already been designed wherein a rolling membermounted on a substantially horizontal fork member pivotally mountedabout a vertical shaft fast with the vehicle determines the conditionsof adhesion existing at any time by measuring the transverse stresseswhich should be applied to this rolling member in order to deviate it,through rotation about this shaft, from a line parallel with thedirection of travel of the vehicle.

The irst object of this invention is to provide, in an adhesionindicator of the type comprising a rolling member acting as a feeler andcarried by .a substantiaily horizontal fork member pivotally mounted ona vertical shaft fast with the vehicle, means ior applying to thisrolling member a torque about the axis of the vertical shaft,

and either the continuous indication of the angular distance existingbetween the actual position of this rolling member submitted to thistorque and ,a predetermined position thereof about the aforesaid axis,or the instantaneous indication that this rolling member is displacedangularly from a predetermined position about the vertical axis.

Another object of the invention is to provide, in an adhesion indicatorof the kind broadly described hereinabove, a member resilientlyconnected to the rolling member for producing a torque, the relativeangular position varying with the speed of the vehicle, the rollingmember moving in a direction parallel with that of the vehicle and beingurged towards a skid position by this torque when the adhesion oi theWheel becomes insufficient to counteract this torque, this skid causingthe actuation oi a visual or .audible warning signal.

The accompanying drawings forming part of this speciiication illustratediagrammatically diiierent practical embodiments of the invention givensolely by way of example in order to facilitate the understanding of thevarious objects of the invention as broadly set forth hereinabove.

In the drawings:

Fig. 1 is a vertical axial section of the adhesion indicator, includingthe feeding circuits and direct reading member thereof.

Fig. 2 shows in axial section and at a greater scale a detail of thedevice of Fig. 1.

Fig. 3 is a section of Fig. l taken along line III-III.

Fig. 4 is a modied embodiment of the torque generating device located inthe upper portion of the adhesion indicator illustrated in Fig. 1.

Fig. 5 is a section of IFig. 4 taken along line V-V.

Figs. 6 and 7 are axial sections of a hydraulic circuit reversing devicein its two operative positions, respectively.

Fig. 8 illustrates the application of the reversing device illustratedin Figs. 6 and 7 to the adhesion indicator illustrated in Fig. 1.

Figs. 9 and l0 illustrate the wiring diagram of the electric circuitsprovided for actuating the apparatus, in the case of .a reversible andirreversible pump, respectively.

Fig. 11 is a perspective View illustrating the mounting of the adhesionindicator according to the invention on a passenger car.

Fig. 12 is a vertical axial section of a modified adhesion indicatoraccording to the invention.

Fig. 13 is a cross-sectional View along the line XIII-XIII of Fig. 12.

Fig'. 14 is a section of Fig. 12 taken along iine XIV-XIV before thetire skids.

Fig. 15 is a view similar to Fig. 14 after the tire skids.

Fig. 16 is the wiring diagram of the electric circuit for actuating theapparatus illustrated in Fig. 12 in case a reversible pump is used forthe hydraulic circuit.

Referring now to the apparatus shown in Figs. 1 and 3 the adhesionindicator according to the invention comprises a wheel l mounted onballbearings and fitted with a special tire 2 having preferably an outerdiameter of about 'l1/2 in. The Wheel I is carried by a lightweight fork3, for instance of cast aluminium, keyed at t4 on the endpiece 5 of atube 6 forming the inner tube member of the body of the apparatus. Thetubular member 6 is a sliding t in another tube which in turn isslidably iitted in a further tube S so as to form a telescopic assembly.Preferably these tubes are made of suitable steel material and have anoval cross-section as illustrated in Fig. 13 in order to prevent themfrom rotating in relation to each other. The lower ends of tubes l, areprovided with spacer rings S, lil, respectively, acting as lower guidingmeans 3 for these tubes. The upper portions of tubes 6, are providedwith packing rings Il, I2, respectively, for instance of rubbermaterial. The outer tube 3 is connected through a welded socket memberI3 with a circular-sectioned tube I4 having slidably mounted therein apiston member I5 urged downwards by a coil spring I5.. This tube I4 hasits upper end closed by a screwthreaded cap II formed with a centralbore and adapted to keep in position a ball bearing I8 interposedbetween the tube I4 and a flanged sleeve member I9 fixed to the upperend of a further tube 20 forming the external casing or body of theapparatus. The cap member I1 also forms a rest member for the spring I6.In addition, a spacer ring 3a is fitted between casing 20 andv tube 8.

This construction provides a cavity A formed between piston I5, tubes,I4, 8, l and 6, and endpiece 5; this cavity is connected through a pipe2| to a pump 22 driven by an electrornotor 22a (Figs. 9, which isstarted by actuating ageneral control knob 23. This pump 2-2 isconnected through a pipe 23av to. a. reservoir 24. Thus, when the pumpfeeding circuit is energized by actuating the knob 23,l pump 22 draws afluid, for instance oil, from the reservoir 24 and delivers it. into thecavity or chamber A thereby causing tubes 'I, S-and therefore the wheelassembly I, 2, 3,' fast with tube 6 throughI endpiece 5-to movedownwards. When the tire 2 engages the ground the oil pressure inchamber A tends to lift piston I5 and spring I6 is compressed. Thispressure causes the wheel to be strongly applied against the ground andacts upon the wheel somewhat in the manner of the Suspension springs ofthe car upon the wheels thereof.

As the rigid assembly consisting of tubes 8 and I4 are fixed to the carframe the greater the load carried by the car, the smaller the distancebetween the frame andy ground, and therefore the greater the pressureexerted upon the spring I6.; thus, a greater load is applied on wheel Iand tire 2. The flexibility of spring I5 is so calculated that aconstant ratio is obtained between the loads supported by the car wheelsand wheel I, 2, respectively.

In the central bore of cap4 I'I is fitted a selflubricating ring 21through which extends a shaft 28 providedwith a bearing flange 29 havingfixed thereon a drum 30. Shaft 28 is held at its upper portion by abearing 3l of self-lubricating material, located in the upper casing 32of the device (Fig. 1).

On the other hand said casing 32 houses a direct-current motor having anarmature 33 mounted on shaft 28 and eld windings 34 fixed to said casing32 secured in turn through any suitable means to the anged sleeve memberI9.

Drum 30 is connected through a spiral spring 35v to the upper end oftube I4 through cap l'I. Thus, when rotor 33 is rotated in the windingdirection of spring 35, tube I4 and therefore the movable assembly ofthe apparatus are subjected tor a torque such as to cause the wheelplane to rotate through an angle a in relation to the direction oftravel of the car. Furthermore, drum 3U may be held in a predeterminedposition by actuating a brake band 36 controlled by an electromagnet 31.

The apparatus further comprises an electric COIIaCt-flgel 38 rigidlyConnected to tube I4 through cap I'I, an electric contact-ringer 39resiliently fixed to casing 32 and an electric con- A tact-finger 4Drigidly fixed to said casing 32 (Figs. 1, 3, 9 and 10).

Fig. 9 illustrates the wiring diagram of the electrical circuit of theapparatus in case pump 22 is of the reversible type. The general controlknob 23 is provided with three sliding contacts 4I, 42 and 43 of whichcontacts 4I, 42 are interconnected.

When the apparatus is started, i. e. after the control knob has beenmoved from position F to position O, the circuit connections are suchthat the pump-driving motor 22a is energized from the positive terminalof the battery through sliding contact 42, contact stud '44, closedcontact 45, motor 22a', contact stud 46, sliding contact 43 and negativeterminal of the battery.

Pump 22 is arranged to draw oil from reservoir 24 and deliver it intothe telescopic tube mem bers in order to put the apparatus in operativecondition. The amount of oilQ to be introduced into the tube;l assemblyshouldA be determined beforehand according to the type of car equipped.This is achieved by providing in each reservoir 2,4 a floating piston 25carrying a contact member 26. When the oil level in the reservoirreaches the predetermined limit corresponding to the delivery7 of thisamount Q of oil, contact 26 engages` contact 4l thereby energizing awinding 48 to open contact 45. The latter is constantly urged in itsclosed position by an overcentre spring 49.

Conversely, pump 22 may draw oil from cavity A for delivering it toreservoir 24.

When the control knob 23 is moved back to its original position F,sliding contact 42 firstly engages contact stud 55v and causes winding5I to be energized. Thus, contact 45 is closed and overcentre spring 49holds this contact in its closed position. Then, on reaching position Fthe motor 22a is reenergized but current iiows thereto in the reversedirection through a circuitpositive terminal, sliding contact 42,contact stud 50a, motor 22a, contact 45, contact stud 44, slidingcontact 43 and negative terminal. As the motor rotates in the oppositedirection pump 22 will deliver oil into` reservoir 24.

When the amount of oil Q corresponding to that required for putting theapparatus in operation is transferred contact member 26a carried by thefloating piston 25 engages contact 4l and winding 48 will be energizedthereby opening Contact 45 and the energizing circuit of motor 22a.

In the case where an irreversible pump is used the driving motor thereofrotates always in the same direction and the general control knob 23d(Figs. 8 and 10) is connected with an oil circuit reversing device ofthe type illustrated in Figs. 6 and 7. This reversing device comprises abarrel 52 formed with a central plug bore in which a tapered plug 53 istightly yet movably fitted for rotation about its axis. Moreover, barrel52 isv formed with four pipe-connecting screwthreaded tapered boresconnected through four passages 54, 55, 56 and 51 with the aforesaidplug bore. Passage 54 is connected to the chamber AY of the apparatus,passage 55 coaxial with passage 54 is connected to the delivery side ofpump 22d, passage 56 is connected to reservoir 24 and passage 5'!coaxial with passage 56 is connected to the intake side of the pump(Fig. 8). Passages 54, 5B are interconnected through a further passage58 in which is located a safety valve 59. Tapered plug 53 is formed witha pair of parallel transverse bores 60, 6I having the same interaxialdistance as passages 54, 56, and a pair of intersecting passages 62, 63opening in passages 54, 5l on the one hand, and 55, 56, on the otherhand. Thus, when the plug of the reversing device is moved to theposition in which the cavity A of the apparatus is lled with pressureoil, the following hydraulic circuit is established (Fig. 6)-reservoir2li, passage 56, passage 6|, passage 5'?, pump 22d, passage 55, passage66, passage 541 and cavity A; when the plug is moved to its other oremptying position the following hydraulic circuit is obtained (Fig.7)-cavity A, passage 5d, passage 62, passage 51, pump 22d, passage 55,passage 63, passage 56 and reservoir 25.

1n this case the electric circuit illustrated in Fig. 9 is slightlysimplified as shown in Fig. l0. The motor terminal opposite to thatconnected with contact d5 is permanently connected to the negativeterminal of the battery while contact stud c6 and sliding contact 43 aredispensed with. Both contact studs 56a and i4 are connnected to thepositive terminal of motor 22a. The rest of the circuit is unchanged andits operation requires no further explanations.

Figs. 9, illustrate in their lower portions the electric circuitprovided for controlling the adhesion indicator proper, which operatesas follows:

When the apparatus is switched to its operative condition, i. e. whenknob 23 is moved to position O, current is fed to neld windings 3:1.,from the positive battery terminal through sliding contact lli, contactstud 66, field windings 35, closed main contact 65 and the negativebattery terminal. At the same time the electromagnet winding 6l isenergized and opens the auxiliary contact 66, thus opening theenergizing circuit to electromagnet 3l and causing the brake band 36 tobe released from drum 36. The armature Si! is rotated by eld windings 34and winds up the spiral spring whereby wheel l will assume a givenangular position in relation to the direction of travel. When thisangular displacement cf wheel I has reached a predetermined value a,contact ringer 38 engages the nxed yet resilient contact nger 33 and asa result current flows through the electromagnet winding 55 which opensmain contact 55; therefore the motor neld windings 34 are de-energized.At the same time, electromagnet winding 6? is cie-energized andauxiliary contact 56 is closed to energize the winding of the brake bandoperating electromagnet 3'! and hold drum 33 and therefore armature 33against motion.

lf a good road adhesion is prevailing the spring 35 will be wound to arelatively high degree thereby moving the wheel I to an angular positioncorresponding to the aforesaid angle a and rotating the armature 33through a Very wide angle, whilst bad adhesion requires but a smallangular displacement of armature 33 to bring the wheel l in the desiredposition.

If at a given moment the adhesion of Wheel l improves, the tensionexerted by spring 35 on tube i6 will be insuiiicient and the wheel willmove closer to the direction of travel of the vehicle.

As a consequence of this modified position of wheel i contact finger 38will be moved away from contact finger 39 and electromagnet winding 65ele-energized. The main contact 65 closes and field windings 34 arere-energized. At the same time, electromagnet winding 61 is energizedand opens contact 66 so that the electromagnet 31 becomes inoperative.The brake band 36 is released from drum 36 and immediately afterwardsarmature 33 begins to rotate in order to restore the wheel i to thedesired position.

Conversely, if adhesion is decreasing the tension exerted by spring 35on tube lf3 will be too strong whereby the wheel will tend to deviatefrom the direction of travel of the vehicle.

The rigid contact nger 38 engages contact finger 33 until it engages theother rigid contact nger 40. Thus, electromagnet winding 69 will beenergized in turn and auxiliary contact' 68 is open in order tode-energize the electromagnet winding 3l and release the brake band 36from the drum. The spiral spring may therefore expand and cause drum 36and armature 33 to move back. Thus the wheel is restored to a correctposition while contact nngers 38 and 40 are separated from each otherand the brake band 36 is again tightened around drum 36. Now if itbecomes desirable to reduce the speed of rotation of drum 36 the lattermay be driven in the way illustrated in Figs. i and 5 which is similarto the upper portion of Fig. l and wherein similar parts are designatedby the same reference numbers with the additional letter b. Aselflubricating ring member 2lb is fitted in the central bore of capmember l'lb and engaged by the bottom end of a shaft 2Gb formed with abearing collar portion 25h. On this shaft 28h is mounted for looserotation a drum 36h carrying loose planet pinions 'i6 meshing with aninternally toothed gear ring il fast with the upper casing 32h and a sungear i3 carried by the shaft 28h. This shaft has its upper end held inthe upper casing 3219 by a self-lubricating bearing Sib and carries therotor 3319.

On the other hand, the rotor shaft 28 (Fig. 1) or 26h (Fig. 4i) isconnected through a sheathed cable 'id to a pointer i5 centred on thespeedometer 'i6 of the vehicle, a suitable reduction ratio beingprovided between the speed of rotation of shaft 2'8 and that of pointerl5 by means of reducing gears 'il and i3.

When the adhesion indicator is inoperative the pointer 'i5 is on thezero position.

When the adhesion indicator is operative, if the adhesion is poorarmature 33 and therefore pointer i5 will be rotated through a smallangle; for instance, it may indicate the Figure 50 on the speedometer.Conversely, if the road surface and condition oifer a good grip to thewheels of the vehicle, armature 33 will be rotated through a greaterangle together with pointer i5 which may indicate, for instance, on thespeedometer.

Thus a mere glimpse at the speedometer will enable the driver to knowthe margin of safety available by observing the angular gap between theactual speedometer pointer i9 and the pointer i5 of the adhesionindicator.

In order to prevent mud or dust likely to be detrimental to theoperation of the apparatus from accumulating on the lower telescopicportion thereof a pleated sleeve 8c of flexible material, for instancenatural or synthetic rubber, is fixed on the lower casing or body 26 andfork 3.

Electromagnets 58 and 5l, contact d5, and the various sliding contactsand contact studs controlled by knob 23 are housed within a box B fromwhich issue wires il, lil, H2, H3, H4, |35 and i136. Electromagnets 66,6l and 65, main contact 65 and auxiliary contact 53 are housed within abox C from which issue wires H9 to |24. Contact member 38, motor 34 andelectro- 7 magnet 31 are respectively connected to wire I II throughlines to |18 (Figs. 1,. 9. and 10.).

As illustrated in Fig. 11 the adhesion indicator is xed by means of itsbody 29 to the frame of a vehicle, in this examplea passenger car 8|, inthe vicinity of the rear axle 82 and with the assistance of a suitablefish-plate 83. The object of this particular mounting is to render thepredetermined angle a substantially insensitive to the shape of thetravel line of the vehicle. In

particular in a curve, the rear vehicle axle passing through theinstantaneous center of gyration of the vehicle, the Contact point oftire 2 with road substantially describes a circle centered on saidgyration center, whereby the plane. of wheel I remains very close to theposition which it occupies when the vehicle travels straight ahead. Incarrying out the invention on practical lines it will be advisable onsafety grounds to restrict the measuring to the zone which precedes pureskidding effect. As, on the other hand, the dimensions of tire 2. aresmaller than standard automobile tires so that the tire ofiset effect isreduced accordingly, the angle a should preferably have a value. closeto 6,-'7.

According to a further embodiment of this invention the adhesionindicator, instead of enabling the driver to estimate his margin ofsafety in accordance with his travelling speed, may warn him of theprecise moment in which a skid is likely to begin. A device of this kindis illustrated in Figs. l2, 14 and l5 of the drawings wherein all partssimilar to those shownl in Figs. 1-8 are designated by the samereference numbers to which the latter av is added.

The adhesion indicator illustrated in axial section in Fig. 12 isprovided with a feeler assembly similar to that shown in Fig. 1 so thatany description thereof would be superfluous, the same applying on theother hand to the hydrau-lic control device therefor.

On the flanged sleeve member |9a is xed a casing 32a. within which aresecured, on either sides of rectangular diameters, four electromagnets85, 86, El and 88. The cores 89, 90, 9| and 92 of these electromagnetsare so disposed that when energized cores 89, 9| will pull on a pair ofpins4 93, 94 fast with a plate 94| fixed on the top surface of capmember I'Ia whilst cores 90, 92 will push these pins (Figs. 14 and 15).The windings 95, 95, 91 and 98 of these electromagnets4 are seriesparallel connected to an electric generator 99 rotating at a speedvarying with the speedv of the vehicle, for instance the generatornormally fitted on the vehicle for lighting and battery chargingpurposes.

Besides, plate '84 is provided with a contact I 99 adapted to engage axed contact IDI carried` by the upper casing 32a of the apparatus whenlate |34. has been displaced angularly from a predetermined position,for instance wherein wheel I is parallel to the direction of travel ofthe vehicle.

When Contact |09 engages Contact IGI it closes an electric circuitconnected tol an optical or sound Warning signal |63.

Fig. 16 illustrates in its lower portion` the electric control circuitof the adhesion indicator shown in Fig. 12. This circuit operates asfollows:

When theY apparatus is put in its operative condition the control knob,23a. closes the energizing circuit for electromagnet windings 95 to 98through engagement of contact, members |94, |05. When the car is inmotion the` generator 99 of the lighting and ignition system thereofenergizes these electromagnet windings to 98. Windings 95 to 98 willattract cores 89 to 92 respectively with a force varying in proportionwith the car speed. As these cores are operatively connected with pins93 and 94 they will apply through the medium of plate 84 a torque to thetelescopic assembly |411, 8a, 'Ia and 6a which will also vary with thetravel speed and tend to rotate wheel Ia about the axis of thistelescopic asembly through the lever arm formed by fork 3a. As long asWheel Ia adheres sufficiently to the road surface this will prevent theaforesaid pivotal effect (Fig. 14), but when low adhesion conditionsprevail, notably when the car speed tends to rise towards a given valueor if the car is insufficiently loaded, wheel Ia will skid and yield tothis torsion torque. Then the diametral pin line 93-94 will tend to takethe slightly inclined position shown in Fig. 15. A slight angulardisplacement of plate 84` will cause contact nger |60 to engage. contactnger ||I| and therefore the circuit for feeding the warning signal |93with current will be closed and the driver warned that the car speed isto be reduced. Although the warning signal |93 is a lamp in Fig. 16 ofthe drawings, it will be readily understood by those conversant with theart that any desired type of visual and/or audible signal may be usedfor this purpose.

Electromagnets 48 and 5|, contact 45, and the various sliding contactsand contact studs controlled by knob 23 are housed within a box E fromwhich issue wires |25 to |32, |35 and |36. Warning device |03 isconnected to contact |0| through wire |33, while generator 99 isconnected to the series parallel electromagnets through wire |34 (Figs.12 and 16).

While I have herein shown and described some forms in which my inventionmay be embodied. it will be understood that the construction thereof andthe arrangement of the variousl parts may be altered without departingfrom the spirit and scope thereof. Furthermore, I do not wish to beconstrued as limiting my invention to the specic embodimentsillustrated, excepting as may be limited in the appended claims.

What I claim is:

1. In an adhesion indicator for automotive Vehicles of the typecomprising a hollow vertical body xed to the frame of the vehicle, avertical supporting member adapted to pivotally move about the verticalaxis of said hollow body, a radially mounted arm at the lower end ofsaid supporting member and a rolling member. rotatably carried by theouter end of said arm and adapted to engage the road surface on whichsaid vehicle is travelling, in combination, a vertical supporting membercomprising a series of telescopic interfltting tubes, the lower partv ofthe tube having the smallest diameter being connected to theradially-mounted arm whilst the upper portion of the tube having thelargest diameter is cylindrical, packing rings respectively interposedbetween said telescopic interfltting tubes, bearing means positionedbetween said large-diameter tube and the vertical hollow body, a pistonreciprocably movable in the cylindrical part of said large-diametertube, a cap member for closing the upper portion of said large-diametertube, a coil spring placed between said piston. andl said cap member,means for filling thel telescopic cavity formed by said telescopic tubesand said piston with an amount of fluid the value of which ispredetermined according to the type of automotive vehicle equipped withthe adhesion indicator for developing the telescopic interfitting tubesand compressing the coil spring with a view to apply the rolling member'against the road surface with a force in proportion with the loadcarried by the wheels of said vehicle, said filling means acting also asdraining means for retracting said adhesion indicator when inoperative,a torque generator carried by the hollow vertical body and connectedwith said supporting member for applying to said last member and to therolling member a torque about the pivotal axis of said supportingmember, and means for determining the road adhesion conditions of thevehicle from the variation in the angular position of said rollingmember with respect to the travel direction of the vehicle from apredetermined position while said member is submitted to the action ofsaid torque generator.

2. An adhesion indicator for automotive vehicles, according to claim 1,wherein the means for filling and draining the telescopic cavitycomprise a reversible pump connected to an orice formed in thelarge-diameter tube, a fluid reservoir connected to said reversiblepump, a reversible motor connected with said reversible pump for drivingthe same, means for rotating said motor in both directions, means forstopping said motor rotating in the direction for which the pump nllsthe telescopic cavity with fluid as soon as the amount of fluid drawn bythe pump from said reservoir reaches a predetermined value, and meansfor stopping said motor rotating in the reverse direction for which thepump drains the telescopic cavity as soon as the amount of iiuiddirected by the pump to said reservoir reaches a predetermined value.

3. An adhesion indicator for automotive vehicles, according to claim 2,wherein the reversible motor is an electric motor and wherein the motorstopping means comprises a floating piston movable in the reservoir, apair of spaced electric contact members fast with said floating piston,a motor-actuating electric circuit having a main contact normally closedwhen said motor is put under tension, a stopping electric circuit havinga winding adapted to open said main contact when energized, and aclosing contact inserted in series in said stopping electric circuit andplaced between said contact members in order to open saidmotor-actuating circuit when either oi said contact members engages saidclosing contact whereby said winding is energized.

e. .an adhesion indicator for automotive vehicles, according to claim l,wherein the means for iilling and draining the telescopic cavitycomprise an irreversible pump connected to an orifice formed in thelarge-diameter tube, a fluid reservoir connected to said irreversiblepump, a motor connected with said pump for driving the same, means forrotating said motor, means for modifying the fluid circuit between thetelescopic cavity and the reservoir for allowing either the filling orthe draining of said cavity, means for stopping said motor when thefluid circuit allows the pump to ll the telescopic cavity as soon as theamount or" fluid drawn by said pump from said reservoir reaches apredetermined value, and means for stopping said motor when the modifiedf circuit allows the pump to drain said telesccpic cavity as soon as theamount of fluid directed by said pump to the reservoir reaches apredetermined value.

5. An adhesion indicator for automtive vehicles, according to claim 4,wherein the motor is an electric motor and wherein the motor stoppingmeans comprises a floating piston movable in the reservoir, a pair ofspaced electric contact members fast with said floating piston, amotor-actuating electric circuit having a main contact normally closedwhen said motor is put under tension, a stopping electric circuit havinga winding adapted to open said main Contact when energized, and aclosing contact inserted in series in said stopping circuit andpositioned between said contact members in order to open saidmotor-actuating circuit when either of said contact members engages saidclosing Contact whereby said winding is energized.

6. An adhesion indicator for automotive vehicles, according to claim 1,wherein the means for filling and draining the telescopic cavitycomprise an irreversible pump having an inlet and an outlet, a fluidreservoir, a motor connected to said pump for driving the same, meansfor rotating said motor, a barrel formed with a central plug bore andwith four connecting radial passages opening in said plug bore andcommunieating with the telescopic cavity through an orice formed in thelarge-diameter tube, the outlet of the pump, the reservoir and the inletof said pump, respectively, a pivotable plug housed in said plug boreand formed with a first pair of bores which, for a first position of thepivotable plug, respectively connect the telescopic cavity passage withthe pump outlet passage and the reservoir passage with the pump inletpassage, said` plug being also formed with a second pair of bores which,for a second position of the pivotable plug, respectively connect thetelescopic cavity passage with the pump inlet passage and the reservoirpassage with the pump outlet passage, means for pivoting said pivotableplug, means for stopping said motor when the pivotable plug is set inthe rst position as soon as the amount of iluid drawn by the pump fromsaid reservoir reaches a predetermined value, and means for stoppingsaid motor when the pivotable plug is set in the second position as soonas the amount of iluid directed by the pump to said reservoir reaches apredetermined value.

'7. An adhesion indicator for automotive vehicles, according to claim 1,wherein the telescopic tubes have an elliptic cross-sectional prole andthe uppermost tube is fast with the cylindrical tube.

8. An adhesion indicator for automotive vehicles, according to claim 1,wherein the ilexibility of the coil spring is so calculated that theloads supported by the rolling member and by the tires of the vehicle,respectively, are kept to a constant ratio.

9. An adhesion indicator for automotive vehicles, according to claim 1,wherein the means for determining the road adhesion conditionscornprises means for moving the rolling member set in operative positionto a predetermined angular position with respect to the directionof'travel of the vehicle under the action of the torque generator whichthen generates a torque the value of which depends on the actual roadadhesion, means for varying the value of said torque to restore saidrolling member to said predetermined angular position when deviatedtherefrom in consequence of a variation in the road adhesion withrespect to the initial road adhesion, and means for indicating the valueof the torque variation as a function of the variation in the angularposi- 11 tion of said rolling member from said predetermined angularposition.

10. An adhesion indicator for automotive vehicles, according to claim 1,wherein the torque generator and the means for determining the roadadhesion conditions comprise va direct-current motor having fieldwindings fast with the hollow vertical body, a shaft journaled forrotation in the cap member closing the telescopic cavity and an armaturekeyed on said shaft, a line connecting said motor with the directcurrent source of the vehicle and having a main contact, resilient meansconnecting said armature and the supporting member, means for lockingsaid armature in rotation, means for closing said contact when the roadadhesion is to be determined, the rolling member being set in operativeposition, whereby said rolling member is driven in rotary movement aboutthe pivotal axis of the supporting member while said resilientconnecting means is tensioned, means for actuating said locking deviceas soon as said rolling member reaches a predetermined angular positionwith respect to the direction of travel of the vehicle and forsimultaneously opening said main contact, means for unlocking saidlocking means and for simultaneously closing said main contact when theangular position of said rolling member comes nearer to said directionof travel due to an improvement of the road adhesion to restore saidrolling member to said predetermined angular position by the subsequentrotation of said armature and tensioning of said resilient means, meansfor unlocking said locking means when the angular position of saidrolling member deviates from Asaid predetermined angular position fordeparting from said direction of travel due to a decreasing 'of the roadadhesion with a View to restore said rolling member in saidpredetermined angular position by the release of said resilientconnecting means, and means for indicating the valueof the variation inthe tension applied to said resilient connecting means as 'a function ofthe variation in the angular position of said rolling member from saidpredetermined angular position.

11. An adhesion indicator for automotive vehicles, according to claim10, wherein the means indicating the tension variation-comprises aflexible cable connected to the 'shaft of the motor, a pinion drivemounted on the speedometer of the vehicle and vcomprising a drivingpinion connected to said iexible cable and a driven vpinion centered onthe pointer shaft of said speedometer, and an adhesion indicator pointer'fast with said driven pinion. y

12. An adhesion indicator for automotive vehicles, according to claim10, wherein the locking, unlocking and resilient connecting meanscomprise a brake drum secured on the motor shaft, a spiral spring theends of which are respectively connected with said drum and with the capmember closing the telescopic'cavity, a brake band surrounding saiddrum, a first electromagnet adapted to tighten said brake band aroundsaid drum when-energized, a`n electromagnet-actuating line having anauxiliary contact and connecting said iirst electromagnet with thecurrent source, a second electromagnet adapted to open said auxiliarycontactand 'mounted in parallel with the motor,'a third Aelectromagne-:tVadapted to open said auxiliary contact when energized and connectedwith one pole Aof the current source, a fourth electromagnet adapted toopen the main contact 'when venergized `and vconnected with the samepole of the current source, a rst contact linger rigidly connected tothe large-diameter tube and connected with the other pole of the currentsource, a second contact iinger fast with the hollow vertical body andconnected With the third electromagnet, and a third contact ngerresiliently mounted with respect to said hollow vertical body andconnected with said fourth electromagnet, said third contact fingerbeing inserted between said rst and second contact ingers withoutcontacting the same when the rolling member is parallel to the directionol travel of the vehicle.

13. An adhesion indicator for automotive vehicles, according to claim10, wherein the locking, unlocking and resilient connecting meanscomprise a brake drum mounted for loose rotation on the motor shaft,planet pinions journaled in said drum, a sun gear fast with and`concentric to said shaft while meshing with said planet pinions, aninternally toothed gear ring fast with the hollow vertical body andmeshing with said planet pinions, a spiral spring the ends of which arerespectively connected with said drum and with the cap mem-ber closingthe telescopic cavity, a brake band surrounding said drum, a rstelectromagnet adapted to tighten said brake band around said drum whenenergized, an electromagnet-actuating line having an auxiliary contactand connecting said first electromagnet with the current source, asecond electromagnet adapted to open said auxiliary contact and mountedin parallel with the motor, a third electromagnet adapted to open saidauxiliary contact when energized and connected with one 'pole of thecurrent source, a fourth electromagnet adapted to open the main contactwhen -energized and connected with the same pole of the current source,a iirst contact finger rigidly connected to the large-diameter tube andconnected with the other pole of the current source, a second contactinger fast with the hollow vertical body and connected with the thirdelectromagnet. and a third contact finger resiliently mounted withrespect to said hollow vertical body and connected with said fourthelectromagnet, said third contact finger being inserted between saidAiirst and second contact fingers without contacting the same when therolling member is parallel to the direction of travel of the vehicle.

14. An adhesion indicator for automotive vehicles, according to claim 1,wherein the means for determining the road adhesion conditions comprisesmeans for varying the torque generated by the torque generator in directratio with lthe vehicle speed, the rolling member -being 'parallel tothe direction of travel of the vehicle, 4and warning rmeans connectedwith the support member and operated thereby as soon as said rollingYmember tends to assume an angular position with respect'to saiddirection of travel under the action of said variable torque, wherebyprevailing low adhesion conditions are indicated.

1'5. An adhesion indicator for automotive vehicles, according to claiml, wherein the torque generator and the means for determining the roadadhesion conditions comprise four series parallel connectedelectromagnets fast with the hollow vertical body and disposedsymmetrically with respect A'to two -rectangular planes passing throughthe vpivotal axis of the supporting member, the-cores of saidelectromagnets being aligned two Vby-two along two tangents of a.commoncircle and moving in the same circular direction when saidelectromagnets are simultaneously energized, means for connecting thetwo pairs of aligned cores with said supporting member, a rst electriccircuit connected to the generator of the vehicle and to saidelectromagnets, whereby the energization of said electromagnets andtherefore the resulting torque applied to said supporting member Variesin direct ratio with the travelling speed of the vehicle, a secondelectric circuit connected to said generator, a warning device insertedin said second circuit, and a contact nger fast with said supportingmember and adapted to close said second circuit when the 14 rollingmember is caused by the influence of the variable torque applied to saidsupporting member to move angularly about the pivotal axis of saidsupporting member from a position parallel 5 With the line of travel ofthe Vehicle.

References Cited in the file of this patent UNITED STATES PATENTS 10Number Name Date 2,269,305 Bell Jan. 6, 1942 2,290,618 Bosomworth July21, 1942 2,441,993 Dasher May 25, 1948 2,496,405 Foufounis Feb. 7, 1950

